Automatic transmission system having a variable speed changing point

ABSTRACT

An automatic transmission system in which the factor related to the load on the engine such as the degree of depression of the accelerator pedal, the negative pressure in the air intake pipe or the slippage of the torque converter and the factor related to the revolution of the engine such as the velocity of air flow into the engine or the number of revolutions of the input shaft of the transmission are the main factors for determining the speed changing point, and speed changing instructions are issued by an electrical control device including a logical operation circuit and transistor relay circuit. In the system, the settings such as the slip ratio of the torque converter, the vehicle speed and the number of revolutions of the engine for determining the speed changing point are changed over by switch means which is manipulated as is desired.

United States Patent- Toyoda et al. [4 Sept. 26, 1972 [54] AUTOMATIC TRANSMISSION SYSTEM 3,439,564 4/1969 Scholl et al ..74/866 HAVING A VARIABLE SPEED 3,448,640 6/1969 Nelson ..74/866 CHANGING POINT 2,995,949 8/l96l Gelenius et al ..74/866 [72] Inventors: Em Toyoda Toyota shi; Masaaki 3,354,744 11/1967 Kuhnle et al ..74/866 X Noguchl, C 05am" FOREIGN PATENTS OR APPLICATIONS Toyota-shI, all of Japan 446 979 I 5/1936 G B 74/73 t t l [73] Assignees: Nippondenso Kabushiki Kaisha, a n am Kariya-shi, Aichi-ken; Toyota Prim ry Examiner-Carlton R. Croyle K Kabushlkl Kasha Assistant Examiner-Thomas C. Perry Oyo apan Attorney-Cushman, Darby & Cushman [22] Filed: Nov. 10, 1969 21 Appl. No.: 875,070 [57] ABSTRACT An automatic transmission system in which the factor related to the load on the engine such as the degree of [30] Forelgn Apphcauon Pnomy Data depression of the accelerator pedal, the negative pres- March 25, 1969 Japan ..44/22826 sure in the air intake pipe or the slippage of the torque converter and the factor related to the revolution of U.S. the engine such as the velocity of air flow into the en- Cl. 3 gine or the number of revolutions of the input Shaft of [5 8] held of Search.... ..74/73], 645, 866 the transmission are the main factors f determining the speed changing point, and speed changing instruc- [56] References C'ted tions are issued by an electrical control device includ- UNTED STATES PATENTS ing a logical operation circuit and transistonrelav circuIt. In the system, the settIngs such as the slIp who of 2,498,600 2/1950 Brunken ..74/645 X the torque converter, the vehicle Speed and the 2,529,129 ll/l950 Blair ..74/73l number f revolutions f the engine f determining 3,007,351 ll/l96l HIlpert ..74/731 X the Speed changing point are changed over by Switch 3,068,715 12/1962 Brennan et al ..74/866 X means which is manipulated as is 3,122,940 3/1964 Shimwell et al. ..74/866 3,301,085 l 1967 De Castelet ..74/866 3 Claims, 32 Drawing Figures PATENTED 3.693.479

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ATTORNEY PATENTED SEP 2 6 I972 SHEET 020! 16 PATENTEDsEP2s 1912 SHEET OBUF 16 PATENTED SEP 2 5 I972 SHEET UQUF 16 PATENTEI] SEP 2 6 I972 SHEET USUF 16 PATENTED SEP 2 6 m2 SHEET 130$ 16 SHEET PATENTEDSP26 I972 AUTOMATIC TRANSMISSION SYSTEM HAVING A VARIABLE SPEED CHANGING POINT This invention relates to a transmission system for automotive vehicles and the like, and more particularly to an automatic transmission system comprising a hydraulic torque converter and multi-speed gear transmission means.

In an automatic transmission system employed heretofore in common passager cars, the speed changing point is generally determined from a signal representing the vehicle speed (taken from the output shaft of a multi-speed gear transmission means) or a signal representing the revolution of the prime mover or internal combustion engine and a signal representing the negative pressure (boost pressure) in the air intake pipe of the internal combustion engine or a signal representing the amount of depression of the accelerator pedal actuated by the driver. A commonly employed method comprises obtaining these signals in the form of a high and a low hydraulic pressure, determining the speed changing point on the basis of the interrelation between these two hydraulic pressures, and opening and closing related valves for selectively hydraulically operating an actuator such as a multiple disc clutch and a brake band. Thus, in the conventional automatic transmission system which is wholly controlled by means of hydraulic pressure, the detected signals in the form of hydraulic pressures are subjected to errors and are therefore generally inaccurate. This means that the speed changing point is also frequently subjected to error. Further, the hydraulic actuating circuit is generally complex and it is not an easy matter to impart thereto an improved function over the existing function. For example, when the vehicle going up a relatively steep slope encounters a relatively gentle incline, a slight release of the depression pressure imparted to the accelerator pedal for the purpose of maintaining the vehicle speed requires gear changing into high gear. Then when the vehicle encounters a steep incline, depression of the accelerator pedal for the purpose of maintaining the vehicle speed would not cause gear changing into low gear until the vehicle speed is considerably reduced, thus putting the drivers inconvenience.

Moreover, when the vehicle is running on a level road or going down a gentle decline, the depression of the accelerator pedal for the purpose of acceleration would not cause gear changing into high gear until the vehicle speed becomes substantially equal to that developed while going up the slope and a gear changing under such circumstances is quite unsatisfactory in that considerable noise is developed from the engine and transmission means. Further, the load on the road-engaging wheels varies depending on variations in the number of passengers or weight of goods carried by the vehicle and on whether the vehicle runs in an urban area or in a suburban area, and similarly unsatisfactory gear changing results. This is because the speed is changed on the basis of a predetermined single speed changing diagram for all of the conditions including going up a steep slope, going down a steep decline, abrupt acceleration on a level road, moderate acceleration on a level road, running on a level road at a constant speed, and a great variation in the load during running in an urban area and running in a suburban area. In other words, the above difficulties arise from the fact that a speed changing line which is satisfactory for an intermediate load and which can deal to a certain extent with a large and a small load is not selected.

Generally, such difficulties are avoided by manually changing the gear means into low gear and preventing it from shifting to high gear.

It is a primary object of the present invention to provide an automatic transmission system having a torque converter, transmission unit and a hydraulic actuating circuit, said system comprising an electrical control device for determining the speed changing point from the revolution of the internal combustion engine and the negative pressure in the air intake pipe or the speed of revolution of the engine and the slip ratio or the like of the torque converter for controlling a distributing valve in said hydraulic actuating circuit, and switch means associated with said electrical control device, said switch means being capable of varying the setting of said electrical control device so as to vary the speed changing point (line) to deal with great variations in the load.

The present invention is featured by the fact that, in an automatic transmission system of the kind in which the factor related to the load of the engine, such as the degree of depression of the accelerator pedal, the negative pressure in the air intake pipe or the amount of slip of the torque converter and the other factors related to the revolution of the engine such as the velocity of air flowing into the engine and the revolution of the input shaft of the transmission unit serve as the main factors for determining the speed changing point, and an electrical control device including a logical operation circuit or transistor relay circuit delivers speed changing instructions, the settings for determining the speed changing point in the electrical control device such as the slip ratio of the torque converter, the vehicle speed and the revolution of the engine are varied in response to the switching operation by switch means depending on a variation in the condition of the road surface or in the weight of goods carried by the vehicle or on whether the vehicle is running in an urban or suburban area. According to the present invention, therefore, the transmission unit is not continuously fixed at a low gear position when it is so set unlike the prior case of manually shifting the gear to low gear, and gear changing from low to high gear is effected any time depending on the value of the speed changing point determining factors so as to enable running in the most appropriate gear position.

In the present invention, an electrical control device is employed to control the distributing valve in the hydraulic actuating circuit as described above. Accordingly, the speed changing point can be determined with high precision and the necessary setting can easily be obtained. Further, switch means is connected with the electrical control device to vary the setting of the electrical control device by the switching operation of same. Accordingly, the required speed changes can be realized exactly by merely varying the speed changing point. Thus, mere addition of the switch means to the electrical control device without appreciably varying the arrangement of the electrical control device provides an inexpensive automatic transmission system of a relatively simple structure.

In the present invention, the electrical control device is composed of revolution setting operating circuits, slip operating circuits and logic circuits for actuating the distributing valve in the hydraulic actuating circuit. Thus, an automatic speed change can satisfactorily be effected even in the case of engine braking in which case the driving force is transmitted from the wheels to the engine and the speed changing point in the case of engine braking can be selected as desired.

FIG. 1 is a sectional view of a transmission unit preferably used in an automatic transmission system embodying the present invention.

FIGS. 2, 3, 4 and 5 are diagrammatic views illustrating the operation of a hydraulic actuating circuit when the present invention is applied to a two-forward speed automatic transmission system, in which the hydraulic actuating circuit is shown in its N, DL, DH and R states, respectively.

FIGS. 6a and 6b are graphs showing two forms of the speed changing region before and after the speed changing points are varied, respectively.

FIG. 7 is a block diagram showing the structure of an electrical control device preferably used in the embodiment of the present invention.

FIGS. 8a and 8b are a side elevational view and a front elevational view, respectively, of a revolution detector preferably used in the device.

FIG. 9 is a block diagram showing the structure of a revolution operating circuit in the device shown in FIG. 7.

FIGS. 10a to 100 are graphic illustrations of the operating voltage waveforms in the revolution operating circuit shown in FIG. 9.

FIGS. 11a and 11b are a block diagram and a circuit diagram, respectively, showing the structure of a slip operating circuit included in the device shown in FIG. 7 and having a variable setting.

FIG. 12 is a block diagram showing the structure of a revolution setting operating circuit included in the device shown in FIG. 7 and having a variable setting.

FIG. 13 is a block diagram showing the structure of a synchronous timing holding circuit in the device shown in FIG. 7.

FIGS. 14a to 14d are graphic illustrations of the operating voltage waveforms in the synchronous timing holding circuit shown in FIG. 13.

FIG. 15 is a block diagram of a bistable memory circuit in the device shown in FIG. 7.

FIGS. 16a to 160 are graphic illustrations of the operating voltage waveforms in the bistable memory circuit shown in FIG. 15.

FIG. 17 is a block diagram illustrating the manner of logical operation for gear changing from low to high gear under both a light and a heavy load.

FIG. 18 is a block diagram illustrating the manner of logical operation under a continuous synchronous timing holding signal after gear changing from low to high gear.

FIG. 19 is a block diagram illustrating the manner of logical operation under the disappearance of the synchronous timing holding signal after gear changing from low to high gear.

FIG. 20 is a block diagram illustrating the manner of logical operation when the slip ratio is reduced to a value less than 0.6 or 0.7 in the course of gear changing from high to low gear.

FIG. 21' is a block diagram illustrating the manner of logical operation under a continuous synchronous timing holding signal after gear changing from high to low gear.

FIG. 22 is a block diagram illustrating the manner of logical operation under the disappearance of the synchronous timing holding signal after gear changing from high to low gear.

A two-forward speed automatic transmission system will be taken as a typical example of the present invention and its structure and function will be described in detail hereunder. It will be understood, however, that the present invention is in no way limited to such a twoforward speed automatic transmission system and is similarly applicable to a three or more forward speed automatic transmission system.

STRUCTURE OF A TWO-FORWARD SPEED TORQUE CONVERTER TRANSMISSION UNIT Referring to FIG. 1, the two-forward speed torque converter transmission unit comprises a hydraulic torque converter 10, a front clutch 20, a rear clutch 30, a rear brake 40 and a gear train 50. At the input side of the hydraulic torque converter 10, the rotary output shaft of an engine (not shown) is directly connected to a shaft 11 which is in turn directly connected to a torque converter pump 12. The torque converter 10 includes the torque converter pump 12, a torque converter turbine 13 disposed opposite to the pump 12, and a stator 15 disposed between the pump 12 and the turbine 13. The stator 15 is provided with a one-way clutch 16. Since the operation of these elements is well known in the art, any detailed description will not be given herein. The torque converter pump 12 discharges a circulating flow of hydraulic fluid and the torque converter turbine 13 is driven by the momentum of such a circulating flow to transmit a driving force to the shaft 14 of the torque converter turbine 13. Thus, a difference exists between the rotation of the torque converter pump 12 and the rotation of the torque con verter turbine 13 and the rotating force is transmitted with such a rotational difference. With a small rotational difference, a small torque is transmitted, while with a large rotational difference, a large torque is transmitted. The torque converter 10 performs the function of transmitting a varying rotational force. According to another expression, the rotational difference is expressed by a revolution ratio or slip ratio.

A hydraulic pump 17 which may be a gear pump is directly connected to the pump shaft 11 for a purpose which will be described later. The front clutch 20 is composed of a clutch drum 21 connected integrally with the turbine shaft 14, a multiple disc clutch 22, a clutch piston 23, a spring plate 24 and a clutch shaft 25. When an actuating hydraulic pressure is applied to the clutch piston 23, the clutch 22 acts to couple the shaft 14 of the torque converter turbine 13 to the clutch shaft 25.

The rear clutch 30 is composed of a clutch shaft 35 connected integrally with the clutch drum 21, a clutch drum 31, a multiple disc clutch 32, a clutch piston 33 and a spring plate 34. When an actuating hydraulic pressure is applied to the clutch piston 33, the clutch 32 acts to couple the clutch drum 21 to the clutch drum 31.

As shown in FIG. 2, the rear brake 40 is composed of a brake piston 41, a brake link 42, a brake band 43, a return spring 44 and a brake cylinder 45. When an actuating hydraulic pressure is applied to the brake cylinder 45, the brake band 43 is actuated to lock a carrier 58 of the gear train 50 against any rotation relative to the housing 18.

These clutches and the brake are similar to those well known in the art. In regard to the gear train 50, it is composed of, for example, a first sun gear 51, a second sun gear 57, a third sun gear 55, first planetary gears 52, second planerary gears 54, an output shaft 56 and a carrier 58. That is, the gear train 50 is in the form of a planetary bevel gear mechanism in which the first sun gear 51 and the second sun gear 57 are disposed opposite to each other tomesh with each other through the first planetary gears 52, and the second planetary gears 54 are integral with the first planetary gears 52 so as to mesh with the third sun gear 55. The planetary bevel gear mechanism takes the following variable speed meshing positions: In high gear, the front clutch and the rear clutch 30 are actuated so that the first sun gear 51 and the second sun gear 57 rotate at the same number of revolutions. In this state, since the car rier 58 is idle, the output shaft 56 is rotated at the same number of revolutions as the two sun gears 51 and 57 and thus rotation is transmitted in a l 1 ratio, as is apparent from FIG. 1. In low gear, the front clutch 20 and the rear brake 40 are actuated so that the rotation at the number of revolutions of the input shaft is imparted to the first sun gear 51, and since the carrier 58 is locked by the rear brake 40 and the second sun gear 57 is idly rotating, the output shaft 56 is rotated at a number of revolutions which is l/K of the number of revolutions of the input shaft. I-lere, K is the speed changing ratio. When reversing, the rear clutch 30 and the rear brake 40 are actuated so that the rotation of the input shaft is imparted to the second sun gear 57, and since the first sun gear 51 is idly rotating and the carrier 58 is locked by the rear brake 40, the output shaft 56 is rotated in the reverse direction at a number of revolutions which is UK of the number of revolutions of the input shaft.

REVOLUTION DETECTING MEANS Means 70 for detecting the number of revolutions of the shaft 1 1 of the torque converter pump 12 comprises a revolution detector 71 (detail of which will be described later) mounted on the housing 18 and a toothed disc 72 mounted on the torque converter pump 12. Suppose that the number of teeth of the toothed disc 72 is n,, then the revolution detector 71 detects an electrical signal S having a frequency which is n times the number of revolutions N, of the torque converter pump 12. Due to the fact that the rotary shaft of the internal combustion engine is integrally connected with the shaft 11 of the torque converter pump 12, the detection of the electrical signal (S n,N,) is equivalent to the detection of the number of revolutions of the engme.

' Means 80 for detecting the number of revolutions of the shaft 14 of the torque converter turbine 13 comprises a revolution detector 81 mounted on the housing 18 and a toothed disc 82 mounted on the front clutch drum 21 which is integral with the shaft 14 of the torque converter turbine 13. The revolution detector 81 may have a structure similar to that of the revolution detector 71, and the toothed disc 82 may also have a structure similar to that of the toothed disc 72. Suppose that the toothed disc 82 has n; teeth, for example, 32 teeth, then the revolution detector 81 detects an electrical signal S having a frequency which is n times the number of revolutions N of the turbine shaft 14. Thus,

S n N- 32 X N In lieu of detection of the number of revolutions of the shaft 14 of the torque converter turbine 13 by the detecting means 80, a value detected at another position, for example, a value detected by a means 90 for detecting the number of revolutions of the output shaft 56 may be operated in a manner as will be described later. Further, the number of revolutions of the shaft 14 of the torque converter turbine 13 may be detected at any point so long as such point is directly connected to the shaft 14 of the torque converter turbine 13.

The means 90 for detecting the number of revolutions of the output shaft 56 comprises a revolution detector 91 mounted on the housing 18 and a toothed disc 92 connected integrally with the output shaft 56. The revolution detector 91 may have a structure similar to that of the revolution detectors 71 and 81. Suppose that the number of teeth of the toothed disc 92 is n;;, for example, n 32, then the revolution detector 91 detects an electrical signal S having a frequency which is n;, times the number of revolutions N of the output shaft 56. Thus, S n N 32 X N The following relation holds between S and S Where K (N /N (speed changing ratio). It will thus be understood that the number of revolutions N of the shaft 14 of the torque converter turbine 13 can be sought from the number of revolutions N of the output shaft 56 by the arithmetic operation described above.

It is possible to eliminate one or the other of the revolution detectors or and their associated input detector circuits 320 or 330 by changing the values of the revolution setting circuits and the slip ratio circuits shown in FIG. 7. For example, by noting as previously described the relationship between N; and N i.e., N KN therefore by substituting the KN wherever an N is shown in FIG. 7, and eliminating the turbine shaft revolution circuit 320 and its associated detector 80 the relationship of the slip ratios and velocity is determined merely by knowing the revolution of the input shaft and the outshaft of the transmission respectively. This can be stated because certain of the circuits are only associated with a first speed operation and certain of the circuits are only associated with a high speed operation, and the logic circuits 590 and 580 respectively indicating low and high gear positions govern the operation of AND circuit 510, and OR and AND circuits 530 and 520 respectively.

Knowing the number of revolutions N of the output shaft 56 enables the speed of the vehicle to be known. Knowing the number of revolutions N of the shaft 11 of the torque converter pump 12 enables the number of revolutions of the engine to be known. Knowing the number of revolutions N of the shaft 14 of the torque converter turbine 13 enables the revolution ratio between the shaft 11 of the torque converter pump 12 

1. An automatic transmission system having a plurality of speed changing regions and including: a transmission unit equipped with an input shaft, a torque converter including a pump operatively connected with the input shaft of said transmission unit and a turbine, speed changing gear means including an input shaft operatively connected with said turbine and frictionally engaging means for accomplishing the selective meshing engagement of gears in the speed changing gear means, a source of fluid pressure, and a hydraulic actuating circuit including a gear position setting valve and a distributing valve for distributing hydraulic fluid from said source to said frictionally engaging means for controlling said frictionally engaging means; said system further comprising first signal generating means, connected to said torque converter pump for generating a signal which is proportional to the rotating speed of said pump, second signal generating means connected to said torque converter turbine for generating a signal which is proportional to the rotating speed of said turbine, an operating circuit including a first revolution variable setting operating circuit connected to said first signal generating means for generating an electrical signal when the signal from said first signal generating means satisfies one of a plurality of settings, a second revolution variable setting operating circuit connected to said second signal generating means for generating an electrical signal when the signal from said second signal generating means satisfied one of a plurality of settings and a variable setting slip operating circuit operative by receiving the electrical output signals from said first and second signal generating means for generating a signal when the ratio between the rotating speeD of said pump and the rotating speed of said turbine satisfies one of a plurality of settings, a logic circuit operative in response to output signals from said operating circuit to actuate the distributing valve in said hydraulic actuating circuit, and switch means connected with operating circuit for changing each one of the settings of said first and second revolution setting operating circuits and said slip operating circuit to another depending on the position of said switch means to effect selection of said speed changing regions.
 2. An automatic transmission system for use with an engine for a vehicle, comprising: a transmission unit equipped with an input shaft and an output shaft, a torque converter including a torque converter pump operatively connected with the input shaft of said transmission unit and a torque converter turbine having an output shaft, speed changing gear means including gears for establishing at least a plurality of forward gear ratios and being connected to said turbine output shaft and including frictionally engaging means for accomplishing the selective meshing engagement of gears in the speed changing gear means of said transmission unit for changing the operative gear ratio of said gears, a source of fluid pressure, and a hydraulic actuating circuit including a gear position setting valve and a distributing valve for distributing hydraulic fluid from said source to said frictionally engaging means for controlling said frictionally engaging means; first signal generating means connected to said torque converter pump for generating a signal which is proportional to engine speed, second signal generating means connected to one of said output shafts for generating a signal which is proportional to vehicle speed, a first revolution setting operating circuit having a plurality of first selectable circuits for effecting different minimum engine speed shift up settings and a plurality of second selectable circuits for effecting different maximum engine speed shift down settings and being connected to said first signal generating means for generating an electrical shift up signal when engine speed exceeds a selected one of said minimum engine speed shift up settings and for generating an electrical shift down signal when engine speed goes below a selected one of said maximum engine speed shift down settings, a second revolution setting operating circuit having a plurality of first selectable circuits for effecting different minimum vehicle speed shift up settings and a plurality of second selectable circuits for effecting different maximum vehicle speed shift down settings and being connected to said second signal generating means for generating an electrical shift up signal when vehicle speed exceeds a selected one of said minimum vehicle speed shift down settings and for generating an electrical shift down signal when said vehicle speed goes below a selected one of said maximum vehicle speed shift down settings, means, including a plurality of torque converter slip ratio determining circuits each having a respective selectable circuit for selecting as between a plurality of slip ratio settings and being connected to both of said generating means, for producing a plurality of complete selectable sets of shift up and down signals for all said forward gear ratios, said plurality of selectable circuits of said first and second revolution setting operating circuits and each of said slip ratio determining circuits being divided into a plurality of sets of selectable circuits with each set containing a different selectable circuit from each of said first and second operating circuits and each of said ratio determining circuits, multiple position switch means connected to each of the said selectable circuits for selecting any one set thereof, and means including logic circuits adapted to be operatively connected to outputs of said selectable circuits and to said distributing valve for operating on the said shift up and down signals resulting form the instant selected complete set of selectable circuits respectively to cause actuation of said distributing valve for an automatic shift up and down in said forward gear ratios.
 3. In an automatic transmission system for use with an engine for a vehicle and of the type including a transmission unit equipped with a torque converter, speed changing gear means including gears for establishing at least a plurality of forward gears ratios and being connected to said torque converter and including frictionally engaging means for accomplishing the selective meshing engagement of gears in the speed changing gear means of said transmission unit for changing the operative gear ratio of said gears, and means for automatically controlling said frictionally engaging means upon receipt of shift signals; the improvement comprising; first signal generating means for generating a signal which is proportional to engine speed, second signal generating means for generating a signal which is proportional to vehicle speed, a first revolution setting operating circuit having a plurality of first selectable circuits for effecting different minimum engine speed shift up settings and a plurality of second selectable circuits for effecting different maximum engine speed shift down settings and being connected to said first signal generating means for generating an electrical shift up signal when engine speed exceeds a selected one of said minimum engine speed shift up settings and for generating an electrical shift down signal when engine speed goes below a selected one of said maximum engine speed shift down settings, a second revolution setting operating circuit having a plurality of first selectable circuits for effecting different minimum vehicle speed shift up settings and a plurality of second selectable circuits for effecting different maximum vehicle speed shift down settings and being connected to said second signal generating means for generating an electrical shift up signal when vehicle speed exceeds a selected one of said minimum vehicle speed shift down settings and for generating an electrical shift down signal when said vehicle speed goes below a selected one of said maximum vehicle speed shift down settings, means, including a plurality of torque converter slip ratio determining circuits each having a respective selectable circuit for selecting as between a plurality of slip ratio settings and being connected to both of said generating means, for producing a plurality of complete selectable sets of shift up and down signals for all said forward gear ratios, said plurality of selectable circuits of said first and second revolution setting operating circuits and each of said slip ratio determining circuits being divided into a plurality of sets of selectable circuits with each set containing a different selectable circuit from each of said first and second operating circuits and each of said ratio determining circuits, multiple position switch means connected to each of the said selectable circuits for selecting any one set thereof, and means including logic circuits adapted to be coupled to said selectable circuits for operating on the said shift up and down signals resulting from the instant selected set of selectable circuits respectively to develop automatic shift up and down signals for connection with said controlling means to cause changes in said forward gear ratios. 